Vacuum cleaner with dirt collection vessel having a stepped sidewall

ABSTRACT

A vacuum cleaner is provided including a nozzle assembly with a suction inlet and a canister assembly. A suction generator and dirt collection vessel ate carried on one of the nozzle assembly and canister assembly. The dirt collection vessel includes a base wall, a stepped sidewall and a dirt collection chamber. The stepped sidewall has a first cylindrical section with a circumference C 1 , and a second cylindrical section with a circumference C 2  where C 1 , C 1 &gt;C 2 . In addition the stepped sidewall includes a step connecting the first and second cylindrical sections where the step and first cylindrical section define an included angle A 1 ≦90°.

TECHNICAL FIELD

The present invention relates generally to the floor care equipment field and, more particularly, to a vacuum cleaner equipped with a dirt collection vessel having a stepped sidewall providing enhanced cleaning efficiency.

BACKGROUND OF THE INVENTION

A vacuum cleaner is an electromechanical appliance utilized to effect the dry removal of dust, dirt and other small debris from carpets, rugs, fabrics or other surfaces in domestic, commercial and industrial environments. In order to achieve the desired dirt and dust removal, most vacuum cleaners incorporate a rotary agitator. The rotary agitator is provided to beat dirt and debris from the nap of the carpet or rug while a pressure drop or vacuum is used to force air entrained with this dirt and debris into the nozzle of the vacuum cleaner. The particulate laden air is then drawn into a dirt collection vessel. The air is then drawn through a filter before being directed through the motor of the suction generator to provide cooling. Finally, the air is filtered to remove any fine particles of carbon from the brushes of that motor or other dirt that might remain in the airstream before being exhausted back into the environment.

Often the dirt collection vessel is designed to produce cyclonic airflow by providing that vessel with a dirt chamber having a cylindrical sidewall and a tangentially directed air inlet. This arrangement forces the air to swirl around the dirt collection chamber in the manner of a cyclone. The centrifugal force that is produced causes dirt and debris to move toward and against the cylindrical sidewall of the chamber while relatively clean air may be drawn off from the center of the chamber through a prefilter toward the main filter and the suction generator.

Under most operating conditions most or all of the dirt and debris is removed from the airstream by the cyclonic airflow. At times, however, some dirt and debris remains entrapped within the airstream. Typically, that dirt and debris is relatively fine dirt particles of light weight which are not as susceptible to the centrifugal separation force produced by the cyclonic airflow.

However, larger debris is sometimes drawn toward and closes some of the airstream apertures provided in the prefilter. In such a circumstance, the cleaning efficiency of the vacuum cleaner becomes impaired.

The present invention relates to a vacuum cleaner equipped with a dirt collection vessel having a stepped sidewall. The stepped sidewall functions to better separate dirt and debris from the airstream by preventing it from being drawn back upwardly in the dirt collection chamber after it settles toward the bottom. As a consequence, any potential for that dirt and debris to be drawn on or into the intake or airstream apertures of the prefilter is greatly reduced or eliminated. The vacuum cleaner therefore operates at peak cleaning efficiency at all times.

SUMMARY OF THE INVENTION

In accordance with the purposes of the present invention as described herein, an improved vacuum cleaner is provided. That vacuum cleaner includes a nozzle assembly with a suction inlet and a canister assembly. A suction generator is carried on one of the canister assembly and nozzle assembly. Similarly, a dirt collection vessel is carried on one of the canister assembly and the nozzle assembly. The dirt collection vessel includes a base wall, a sidewall and a dirt collection chamber. Further, the dirt collection vessel is characterized by the sidewall having a first cylindrical section with a circumference C₁ and a second cylindrical section with a circumference C₂ where C₁>C₂. Further the dirt collection vessel is characterized by a step connecting the first cylindrical section with the second cylindrical section.

More specifically, describing the invention the circumference C₁, is between about 18.8 in. and about 25.1 in. The circumference C₂ is between about 15.7 in. and about 22.0 in. Further the first cylindrical section has a height H₂ of between about 6 in. and about 7 in. The second cylindrical section has a height H₂ of between about 5 in. and about 6 in. Together the circumference C₁ and the height H₁ define a volume V₁ of between about 169.6 in.³ and about 351.9 in.³ while the circumference C₂ and the height H₂ define a volume V₂ of between about 98.2 in.³ and about 230.9 in³. Further the step has a width between the first cylindrical section and the second cylindrical section of between about 0.1 in. and about 2.5 in.

In addition a support is concentrically received in the first cylindrical section. The support projects from the base wall. A prefilter is carried on the support. The prefilter includes a third cylindrical section that carries an angled flange. The flange and the third cylindrical section meet at a vertex V defining an included angle A₂ of between about 135 to about 165 degrees. The vertex V is received concentrically within the second cylindrical section. Further the flange includes a straight, continuous face. An annular gap is provided between the flange and the end of the second cylindrical section. The gap has a width of between about 0.5 in. and about 2.5 in.

Still further, a filter is provided in the dirt collection chamber. The filter is carried on the prefilter. A lid including a top wall closes an end of the dirt collection vessel opposite the base wall. The lid includes an inlet in communication with the dirt collection chamber and an outlet in communication with an upstream side of the filter.

In one possible embodiment the nozzle assembly is pivotally connected to the canister assembly. Further, a rotary agitator may be carried on the nozzle assembly adjacent the suction inlet. In addition the canister assembly may include a control handle.

In accordance with yet another aspect of the present invention, the step between the first cylindrical section and second cylindrical section may include a channel opening toward the base wall. In such an embodiment that channel could be defined by the first cylindrical section, the second cylindrical section and the step. The channel may include an arcuate bottom wall.

In the following description there is shown and described several preferred embodiments of this invention, simply by way of illustration of some of the modes best suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments and its several details are capable of modification in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWING

The accompanying drawing incorporated in and forming a part of this specification, illustrates several aspects of the present invention, and together with the description serves to explain certain principles of the invention. In the drawing:

FIG. 1 is a perspective, partially broken-away view of the floor cleaning apparatus of the present invention;

FIG. 2 is an exploded perspective view of the dirt collection vessel, filter and flow control valve assembly of the apparatus illustrated in FIG. 1;

FIG. 3 is a cross-sectional view of the dirt collection vessel, filter and flow control valve assembly in the first position allowing for normal vacuum cleaner operation;

FIG. 4 is a schematical plan view illustrating the first flow valve in the first position allowing normal vacuum cleaner operation;

FIG. 5 is a cross-sectional view similar to FIG. 3 but illustrating the flow control valve assembly in the second position allowing cleaning of a section of the filter;

FIG. 6 is a schematical plan view similar to FIG. 4 but showing the first flow valve in the second position allowing air to be drawn through the clean air inlet;

FIG. 7 is a detailed top perspective view of the filter assembly;

FIG. 8 is a schematical illustration of an additional filter cleaning feature that may be utilized to clean dirt and debris from the filter in situ in the dirt collection vessel; and

FIG. 9 a-9 c are detailed, schematical illustrations of three possible, embodiments of the stepped sidewall for a dirt collection vessel.

Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawing figures.

DETAILED DESCRIPTION OF THE INVENTION

Reference is now made to FIG. 1 which illustrates the floor cleaning apparatus 10 of the present invention. In the illustrated embodiment, the floor cleaning apparatus 10 comprises an upright vacuum cleaner. It should be appreciated, however, that the apparatus 10 may just as easily be a canister vacuum cleaner or a handheld vacuum cleaner.

As illustrated, the apparatus 10 includes a housing 12 including both a nozzle assembly 14 and a canister assembly 16. The nozzle assembly 14 includes a suction inlet 18 through which air entrained with dirt and debris is drawn into the vacuum cleaner. A rotary agitator 20 is mounted to the nozzle assembly 14 and extends across the suction inlet 18.

The canister assembly 16 includes a handle 22 having a handgrip 24. An actuator switch 26 for turning the vacuum cleaner on and off is provided adjacent the handgrip. In addition the canister assembly 16 includes a cavity or receiver 28 for receiving and holding a dirt collection vessel 30. A suction generator 32 is mounted in a compartment in the canister assembly 16. During operation, the rotary agitator 20 beats dirt and debris from the nap of the rug or carpet being cleaned. The suction generator 32 draws air entrained with that dirt and debris through the suction inlet 18 into the dirt collection vessel 30. The dirt and debris is trapped in the dirt collection vessel 30 and the now relatively clean air passes through and over the motor of the suction generator 32 to provide cooling before being exhausted through an exhaust port (not shown) back into the environment.

As best illustrated in FIG. 2, the dirt collection vessel 30 comprises a dirt cup section 36 and a lid section 38. The dirt cup section 36 comprises a stepped sidewall 35 and a bottom wall 37. The benefits provided by the stepped sidewall 35 will be discussed in greater detail below. The lid section 38 comprises a first element 40, second element 42 and third element 43. The first element 40 includes the dirty air inlet 44 and a filter cavity 46. The second element 42 includes a clean air outlet 48 and a clean air inlet 50.

A filter, generally designated by reference numeral 52, is received in the filter cavity 46 of the first element 40. The filter 52 includes a sidewall 54, a hub 56 and multiple partitions 58 extending between the hub and the sidewall (see also FIG. 7). The partitions 58 serve to divide the filter 52 into multiple sections 60. A filter media 62, of a type well known in the art, extends between the sidewall 54, hub 56 and partitions 58 defining each section 60.

An inner support 64 extends upwardly in the dirt cup section 36 from the bottom wall 37. A prefilter 66 rests on the inner support 64. The prefilter 66 includes a series of intake apertures 68 that allow airflow in a manner that will be described in greater detail below.

In the illustrated embodiment, the dirt collection vessel 30 is designed to produce cyclonic airflow and thereby use centrifugal force to improve the efficiency with which dirt and debris are removed from the airstream. More specifically, as clearly illustrated in FIG. 2, the dirt cup section 36, the lid section 38, the inner support 64, the prefilter 66 and the filter 52 are all substantially cylindrical in shape. As illustrated in FIGS. 3 and 5, the inner support 64 and prefilter 66 are concentrically received in the stepped sidewall 35 of the dirt cup section 36. The filter 52 is concentrically received in the filter cavity 46 of the first element 40 of the lid section 38. The dirty air inlet 44 is tangentially directed into the annular space S formed between (a) the first element 40 and stepped sidewall 35 on the outside and (b) the inner support 64 and prefilter 66 on the inside. The airstream flows around the annular space S in a circular or vortex pattern generating centrifugal force that causes dirt and debris in the airstream to move outwardly toward the stepped sidewall 35 thereby causing the dirt and debris to collect in the dirt cup section 36.

Simultaneously, the relatively clean air is drawn through the intake apertures 68 provided in the prefilter 66 along the inner wall of the annular space S where it is then directed upwardly through the filter 52. Specifically, the air passes through the filter media 62 where any fine dirt and debris remaining in the airstream is stopped while clean air passes through the media on through the clean air outlet 48 to the suction generator 32. The direction of airflow during normal vacuum cleaner operation is shown by action arrows in FIG. 3.

The flow control valve assembly of the present invention is generally designated by reference numeral 70. As best illustrated in FIG. 2, the flow control valve assembly 70 comprises a first flow valve 72 carried by a cooperative valve body 71 that covers the clean air inlet 50. As best illustrated in FIGS. 4 and 6, two first flow valves 72 are each pivotally connected to the valve body 71 by a pivot pin 74. A torsion spring 75 is provided on each first flow valve 72. The torsion springs 75 function to bias the first flow valves 72 into a first position, illustrated in FIG. 4 wherein the first flow valves 72 close the two opposed ports 73.

Each first flow valve 72 includes a first cam follower 76. Each cam follower 76 engages a first cam 78 mounted to or integrally formed on the underside of a first drive gear 80. The drive gear 80 is driven by an actuator. In the illustrated embodiment the actuator comprises a meshing second drive gear 82 and a cooperating stepper motor 84. In alternative embodiments the actuator may comprise, for example, a manual twist knob/finger wheel or an electrical solenoid and activation switch. The operation of the stepper motor 84 and the first flow valve 72 will be described in greater detail below.

As further illustrated in FIG. 2, an air guide 86 is keyed to the first drive gear 80. More specifically, the first drive gear 80 includes a hexagonal shaft 85 that is received in a hexagonal opening 87 provided in the hub 89 of the air guide 86. As should also be appreciated, the air guide 86 includes an inlet 88 and an outlet 90. The inlet 88 extends concentrically around the hub 89 while the outlet 90 projects radially outwardly in an arc of A° (see also FIG. 7).

Referring back to the filter 52, each section 60 also has an arc of A°. In the illustrated embodiment, the filter 52 includes eight partitions 58 dividing the filter 52 into eight equal sections 60, each spanning a 45° arc. Thus, the outlet 90 of the air guide 86 also spans a 45° arc, matching the arc of each individual section 60 of the filter 52. Of course, sections of other sizes could be provided (e.g. 12 sections each having an arc of 30°, 10 sections each having an arc of 36°, 9 sections each having an arc of 40°, 6 sections each having an arc of 60 ).

The flow control valve assembly 70 also includes a second flow valve 92. The second flow valve 92 includes an outer sidewall 94 and a mounting hub 96 concentrically received in that outer sidewall. A second cam 98 is provided on the air guide 86. A cooperating second cam follower 100 engages the second cam 98. The second cam follower 100 includes a mounting shaft 102 having a pointed end 104 and a channel 106. The pointed end 104 is extended into the mounting hub 96 of the second flow valve 92 and that hub engages in the channel 106 so as to secure the second flow valve to the mounting shaft 102.

As further illustrated in FIG. 2, the second cam follower 100 includes a hexagonal head 108. The hexagonal head 108 is received in the hexagonal opening 110 in the first element 40 so that the second cam follower 100 is keyed to the lid section 38 to prevent relative rotation. A coil spring 112 is received around the shaft 102 and held in the hexagonal opening 110 in the hub of the first element 40. The spring 112 biases the second cam follower 100 into engagement with the second cam 98 at all times. As best illustrated in FIGS. 3 and 5, the second flow valve 92 is concentrically received within the prefilter 66. An annular seal 114 is connected between the lower margin of the second flow valve 92 and the wall of the prefilter 66. The annular seal 114 extends fully circumferentially between these two components.

The operation of the flow control valve assembly 70 will now be described in detail. During normal vacuum cleaner operation, the suction generator 32 draws air from the suction inlet 18 through the dirt collection vessel 30 where dirt and debris is trapped and then exhausts clean air from the exhaust port. In order to do this, the flow control valve assembly 70 is positioned as illustrated in FIGS. 3 and 4 so that the first flow valve 72 closes the ports 73 leading to the clean air inlet 50 and the second flow valve 92 opens the annular passage 116 between the angled flange 118 at the top of the second valve 92 and the sidewall of the prefilter 66 so that air may pass from the annular space S through the intake apertures 68 and the filter media 62 of the filter 52 before passing through the outlet 48 to the suction generator 32.

As the vacuum cleaner continues to operate, fine dirt particles not removed from the airstream by the cyclonic action in the annular space S is stripped from the airstream and trapped by the filter media 62 of the filter 52. Over time, these fine dirt particles begin to close off the pores in the filter media 62 thereby restricting airflow. This not only causes the motor of the suction generator 32 to run hotter and at a lower efficiency, it also reduces airflow thereby adversely affecting the cleaning efficiency of the vacuum cleaner. Consequently, the airflow may become so restricted as to prevent the vacuum cleaner from cleaning properly. It is then necessary to either clean or replace the filter 52.

The present invention allows the filter 52 to be cleaned in situ in a very convenient and efficient manner. Specifically, the stepper motor 84 may be activated to rotate the air guide 86 through an arc of 45° by means of the meshing drive gears 80, 82. This functions to rotate the air guide 86 so that the outlet 90 thereof is exactly aligned over or in registration with one of the sections 60 of the filter 52. The rotation of the first drive gear 80 simultaneously causes the first cam 78 to rotate from the position shown in FIG. 4 to the position shown in FIG. 6. As this occurs, the cam followers 76 rise up on the first cam 78 and the first flow valves 72 pivot about the pins 74 opening the ports 73 leading to the clean air inlet 50.

As the stepper motor 84 rotates the drive gear 80, first cam 78 and air guide 86, the second cam 98 is also rotated. The second cam follower 100 rides upward on the cam 98 raising the second flow valve 92 so that the upper edge thereof engages the prefilter 66 above the intake apertures 68 around its full circumference. Thus, it should be appreciated that as the ports 73 open through movement of the first flow valve 72, the second flow valve 92 closes the air passage from the prefilter 66 to the outlet 48. Accordingly, the suction generator 32 draws clean air through the ports 73 and the clean air inlet 50. That air is then drawn through the inlet 88 of the air guide 86 and then directed by the outlet 90 thereof through the single individual section 60 of the filter 52 with which the outlet is aligned. Since the clean air is moving through the selected section 60 of the filter 52 in a direction opposite that of normal operation, dirt (and particularly fine dirt from the pores of the filter), is forced from the filter media 62. The dirt expelled from the section 60 of the filter 52 being cleaned has a tendency to be trapped in the lumen or particle trap 120 of the inner support 64. This is due in large degree to the shape of the support which includes a frustoconical upper end 122 connected to a substantially cylindrically shaped lower end 124 by an intermediate bottleneck section 126 of smaller circumferential opening than the lower end. The relatively clean air is then drawn back through the other sections 60 of the filter 52 not aligned with the outlet 90 of the air guide 86 before passing through the outlet 48 and moving on to the suction generator 32.

As should be remembered, the outlet 90 of the air guide defines an arc only as wide as one section 60 of the filter 52. In the presently illustrated embodiment that section has an arc of 45°. This means the remaining sections of the filter 52 not aligned with the air guide 86 define an arc of 315°. This is a much larger cross-sectional area than the 45° arc through which the air initially passes. The resulting pressure drop helps to insure that dirt and debris cleaned from the section 60 of the filter aligned with the air guide 86 falls out of the airstream downwardly into the particle trap 120 of the support 64 where it is retained. Accordingly, the fine dust and dirt particles cleaned from the selected section 60 of the filter 52 are not thereby deposited on the other sections of the filter during the cleaning cycle.

The cleaning cycle may last, for example, from about 1 to about 30 seconds and more typically from about 3 to about 15 seconds. The stepper motor 84 may then be activated again to rotate the first and second drive gears 80, 82, the first cam 78 and the second cam 98 to thereby move the first flow valves 72 from the open position to the closed position and the second flow valve 92 from the closed position to the open position (i.e. move the flow valves 72, 92 from the positions illustrated in FIGS. 5 and 6 to the positions illustrated in FIGS. 3 and 4). This returns the vacuum cleaner 10 to normal operation where dirt and debris are drawn from the suction inlet 18 through the dirty air inlet 44 into the dirt collection vessel 30. There cyclonic airflow utilizes centrifugal force to efficiently remove dirt and debris from the airstream. That dirt and debris is captured in the annular space S of dirt cup section 36 as relatively clean air is drawn through the intake apertures 68 of the prefilter 66. That air then passes through the passage 116 to the filter 52 where any remaining fine particles are stripped from the airstream before it passes through the outlet 48 and travels to the suction generator 32. The airstream then cools the motor of the suction generator 32 before being exhausted back into the environment through the exhaust port. Of course, it should be appreciated that the stepper motor 84 may just as easily be activated so as to clean any number of the filter sections 60 before returning to normal operation mode, depending on the judgment of the vacuum cleaner operator.

Reference is now made to FIG. 8 schematically illustrating an optional additional feature of the present invention that may be provided to further enhance the cleaning of the filter 52. A clicker 130 may be provided. In the illustrated embodiment the clicker 130 includes an elongated mounting arm 131 that is held on a stub shaft 132 secured to the lid section 38. A resilient flap 134 is provided at each end of the arm 131. As illustrated the tips of the flaps 134 engage the media 62 of the filter 52 between the sidewall 54 and the hub 56. A drive motor 136 is provided. As illustrated in full line in FIG. 8 the drive motor may be connected to the clicker 130 and activated to rotate the clicker with respect to the lid section 38 and the filter 52. As the clicker 130 is rotated, the tips of the flaps 134 engage the peaks of the ribbed filter material 62 thereby vibrating the filter material and effectively loosening dirt and debris from the pores thereof. While the vibration provides good cleaning action when utilized alone, it is particularly effective when utilized with the pneumatic cleaning mechanism previously described in this document.

In an alternative arrangement also illustrated in FIG. 8, the drive motor is connected to the filter 52 (note dash line in drawing FIG. 8). In this arrangement the filter 52 is rotated while the clicker 130 and lid section 38 remain stationary. The result is the same in that the tips of the flaps 134 engage the peaks of the ribbed filter media 62 as the filter is rotated thereby vibrating the media and loosening dirt and debris therefrom.

Reference is now made to FIGS. 9 a-9 c which schematically illustrate three possible embodiments of the stepped sidewall 35. As illustrated in FIG. 9 a, the stepped sidewall 35 of the dirt cup section 36 includes a first cylindrical section 150 and a second cylindrical section 152 connected together by an annular step 154. As illustrated the step 154 and first cylindrical section 150 define an included angle A₁, of 90 degrees.

In the embodiment illustrated in FIG. 9 b, the stepped sidewall 35 again includes a first cylindrical section 150, a second cylindrical section 152 and an annular step 154 that interconnects those two cylindrical sections. In this embodiment the annular step 154 in the first cylindrical section 150 defines an included acute angle A₁, that is, an angle A₁ less than 90 degrees. As a result a channel 156 is formed between the step 154 in the first cylindrical section 150 of the sidewall 35. This channel 156 opens towards the base wall 37 of the dirt cup section 36.

FIG. 9 c illustrates yet another possible embodiment of the stepped sidewall 35. In this embodiment the stepped sidewall 35 includes a first cylindrical section 150, a second cylindrical section 152 and an annular step 154 connecting the first and second cylindrical sections. Together, the cylindrical sections 150, 152 and annular step 154 define a channel 156 that opens toward the base wall 37 of the dirt cup section 36. As illustrated in phantom line at the right side of FIG. 9 c that channel 156 may have an arcuate bottom wall if desired.

In any of the embodiments illustrated in FIG. 9 a-9 c, the first cylindrical section 150 has a circumference C₁ that is between about 18.8 in. and about 25.1 in. The second cylindrical section 152 has a circumference C₂ that is between about 15.7 in. and about 22.0 in. The first cylindrical section has a height H₁, that is between about 6 in. and about 7 in. and the second cylindrical section 152 has a height H₂ that is between about 5 in. and about 6 in. The first cylindrical section 150 therefore defines a volume V₁ of between about 169.6 in.³ and about 351.9 in.³ while the second cylindrical section 152 defines a volume V₂ of between about 98.2 in.³ and about 230.9 in.³. The annular step 154 has a width between the first cylindrical section 150 and the second cylindrical section 152 of between about 0.1 in. and about 2.5 in.

As further illustrated in FIGS. 9 a-9 c, the inner support 64 projects from the base wall 37 and carries the prefilter 66. The prefilter 66 includes a third cylindrical section 158 incorporating the plurality of intake apertures 68 (for simplicity of illustration only eight apertures are shown). An angled flange 160 depends from the third cylindrical section 158. The third cylindrical section 158 and angled flange 160 meet at a vertex V defining an included angle A₂ of between about 135 to about 165 degrees. The vertex V is received concentrically within the second cylindrical section 152: that is, it is positioned above the step 154 in the illustrated embodiments. As illustrated the angled flange 160 also presents a straight continuous face 162. An annular gap 164 is provided between the flange 160 and the end 166 of the second cylindrical section 152. The gap 164 has a width of between about 0.5 in. and about 2.5 in. Further, the geometry of the prefilter 66, first cylindrical section 150 and angled flange 160 are such that the dimension E equals the dimension F.

In any of the embodiments illustrated in FIGS. 9 a-9 c, the stepped sidewall 35 provides for more efficient and effective cyclonic separation of dirt and debris from the airstream. More specifically, air is delivered to the dirt collection vessel 30 through the tangentially directed inlet 44. As a result the airstream moves in a vortex pattern in the annular space S. As a consequence, centrifugal force acts upon dirt and debris in the airstream causing it to move toward the surface of the sidewall 35. As the airstream is forced and moves toward the base wall 37 of the dirt collection vessel 30, the dirt and debris previously flowing against the second cylindrical section 152 crosses the step 154 and begins moving in engagement with the first cylindrical section 150. The annular step 154 in the FIG. 9 a embodiment and the channel 156 in the FIG. 9 b and 9 c embodiments then act as a physical barrier that prevents any dirt and debris moving along the first cylindrical section 150 from rising up to move along the second cylindrical section 152. Thus, dirt and debris is essentially captured in the portion of the dirt collection vessel 30 defined between the first cylindrical section 150, the step 154 and the base wall 37. Consequently dirt and debris is prevented from rising toward the intake aperture 68 in the prefilter 66. As a consequence, dirt and debris is prevented from interrupting or otherwise interfering with the passage of air through the intake aperture 68 and peak cleaning efficiency is provided at all times.

The foregoing description of a preferred embodiment of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. For example, the air guide 86 of the illustrated and described embodiment extends through an arc of A° matching each section 60 of the filter 52. The air guide 86 may in fact have an arc that is a multiple of A° so as to allow the cleaning of more than one section of the filter at one time. Further, the filter cleaning function may be automatic. It may be automatically initiated after a certain time period of operation or upon some event occurring such as the movement of the control handle 22 into the upright or storage position. Further, it should be appreciated that clean air from the suction generator exhaust can be recycled to clean the filter.

The embodiment was chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled. The drawings and preferred embodiments do not and are not intended to limit the ordinary meaning of the claims and their fair and broad interpretation in any way. 

1. A vacuum cleaner, comprising: a nozzle assembly including a suction inlet; a canister assembly; a suction generator carried on one of said canister assembly and said nozzle assembly; a dirt collection vessel carried on one of said canister assembly and said nozzle assembly, said dirt collection vessel including a base wall, a stepped sidewall and a dirt collection chamber; said dirt collection vessel being characterized by (1) said stepped sidewall having a first cylindrical section with a circumference C₁ and a second cylindrical section with a circumference C₂ where C₁>C₂ and (2) a step connecting said first cylindrical section with said second cylindrical section where said step and said first cylindrical section define an included angle A₁≦90°.
 2. The vacuum cleaner of claim 1 wherein said step includes a channel opening toward said base wall.
 3. The vacuum cleaner of claim 1, wherein said first cylindrical section, said second cylindrical section and said step define a channel opening toward said base wall.
 4. The vacuum cleaner of claim 1, wherein said circumference C₁ is between about 18.8 in. and about 25.1 in.
 5. The vacuum cleaner of claim 4, wherein said circumference C₂ is between about 15.7 in. and about 22.0 in.
 6. The vacuum cleaner of claim 5, wherein said first cylindrical section has a height H₁ of between about 6 in. and about 7 in. and said second cylindrical section has a height H₂ of between about 5 in. and about 6 in.
 7. The vacuum cleaner of claim 6, wherein said circumference C₁, and said height H₁, define a volume V₁, of between about 169.6 in.³ and about 351.9 in.³ and said circumference C₂ and said height H₂ define a volume V₂ of between about 98.2 in.³ and about 230.9 in.³.
 8. The vacuum cleaner of claim 1, wherein said step has a width between said first cylindrical section and said second cylindrical section of between about 0.1 in. and about 2.5 in.
 9. The vacuum cleaner of claim 1, further including a support concentrically received in said first cylindrical section and projecting from said base wall.
 10. The vacuum cleaner of claim 9, including a prefilter carried on said support.
 11. The vacuum cleaner of claim 10, wherein said prefilter includes a third cylindrical section that carries an angled flange.
 12. The vacuum cleaner of claim 11, wherein said flange and said third cylindrical section meet at a vertex V defining an included angle A₂ of between about 135 to about 165 degrees.
 13. The vacuum cleaner of claim 12, wherein said vertex V is received concentrically within said second cylindrical section.
 14. The vacuum cleaner of claim 13, wherein said flange includes a straight, continuous face.
 15. The vacuum cleaner of claim 14, wherein an annular gap is provided between said flange and an end of said second cylindrical section, said gap having a width of between about 0.5 in. and about 2.5 in.
 16. The vacuum cleaner of claim 15, further including a filter provided in said dirt collection chamber.
 17. The vacuum cleaner of claim 16, wherein said filter is carried on said prefilter.
 18. The vacuum cleaner of claim 17, wherein a lid including a top wall closes an end of said dirt collection vessel opposite said base wall.
 19. The vacuum cleaner of claim 18, wherein said lid includes an inlet and an outlet.
 20. The vacuum cleaner of claim 18, wherein said inlet is in communication with said dirt collection chamber and said outlet is in communication with an upstream side of said filter.
 21. The vacuum cleaner of claim 1, wherein said nozzle assembly is pivotally connected to said canister assembly.
 22. The vacuum cleaner of claim 1, further including a rotary agitator carried on said nozzle assembly adjacent said suction inlet.
 23. The vacuum cleaner of claim 1, wherein said canister assembly includes a control handle. 